1. Field of the Invention
The present invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium having excellent electromagnetic characteristics and friction characteristics.
The present invention further relates to a magnetic signal reproduction system and magnetic signal reproduction method employing the magnetic recording medium.
2. Discussion of the Background
In recent years, technology to transfer information at high speed have developed markedly, making it possible to transfer images and data comprised of immense amounts of information. As the quantity of such data has increased and data transfer technology has improved, there has been a demand to further increase the recording density and transfer rate of recording and reproduction devices and recording media for recording, reproducing, and storing information.
The use of ferromagnetic powder selected from fine particles and fine dispersion of ferromagnetic powder to make the surface of the magnetic layer smooth are effective ways to increase the recording density and transfer rate. An increase in the sensitivity of the reproduction head commensurate with the increase in high density recording is underway on the recording and reproduction device side. In recent years, higher sensitivity giant magneto resistive head (called “GMR head”) have been proposed. However, when a highly sensitive GMR head is employed as a reproduction head, noise also ends up being detected with high sensitivity.
Accordingly, in systems employing GMR heads as reproduction heads, it becomes necessary to reduce noise on the medium side. Making the magnetic layer surface smooth as set forth above is also effective in this regard. However, the smoother the surface of the magnetic layer is made, the greater the coefficient of friction as the reproduction head slides over the medium becomes, compromising running durability.
One conceivable means of improving the frictional characteristics of the medium is to reduce the area of contact when the head is sliding over the medium by forming protrusions on the surface of the magnetic layer. In this regard, controlling the presence of protrusions on the surface of the magnetic layer is proposed, for example, in Japanese Unexamined Patent Publication (KOKAI) Heisei No. 9-128739 or English language family member U.S. Pat. No. 5,718,964, Japanese Unexamined Patent Publication (KOKAI) No. 2004-326863 or English language family member US 2004/0214048 A1, Japanese Unexamined Patent Publication (KOKAI) Heisei No. 6-52541 or English language family member U.S. Pat. No. 5,512,350, and Japanese Unexamined Patent Publication (KOKAI) No. 2005-216349, which are expressly incorporated herein by reference in their entirety.
However, when protrusions are formed on the surface of the magnetic layer as described in the above-cited publications, despite enhanced running durability, increased spacing between the head and medium ends up compromising electromagnetic characteristics. In addition, the protrusions may cause noise, and when the protrusions are reduced, dynamic friction and static friction increase, making it difficult to achieve stable running. Therefore, conventionally, there has thus been a tradeoff between electromagnetic characteristics and friction characteristics, and it has been difficult to achieve them both.